As image forming apparatuses such as printers, facsimile machines, copiers, plotters, and multi-task machines having plural such functions, ink jet recording apparatuses of a liquid ejection recording type using a recording head that ejects, for example, ink liquid droplets are known. The image forming apparatus of this type ejects ink droplets from the recording head onto a sheet (that is not limited to a paper, but it means one such as an overhead transparency film to which ink droplets and other liquids can be attached and referred to be a medium to be recorded, a recording paper, or a recording sheet) during conveyance to perform image formation (used synonymously with recording, printing, and imaging). Examples of the image forming apparatus include a serial-type image forming apparatus in which the recording head ejects liquid droplets to form an image while moving in a main scanning direction and a line-type image forming apparatus using a line-type head in which the recording head ejects liquid droplets to form an image without moving.
Note that in the present invention, the “image forming apparatus” of the liquid ejection recording type refers to an apparatus that ejects a liquid onto a medium such as a paper, a thread, a fiber, a fabric, leather, metal, a plastic, glass, wood, and a ceramic so as to perform the image formation. Furthermore, the “image formation” refers to forming on the medium not only relevant images such as characters and graphics, but also irrelevant images such as patterns (i.e., liquid droplets are just ejected on the medium). Furthermore, “ink” is not limited to narrowly-defined ink and is not particularly limited so long as it is turned into a liquid when being ejected. For example, the ink refers also to a DNA sample, a resist material, a pattern material, etc.
In the above image forming apparatus, the ink containing a color material is turned into liquid droplets to perform the image formation. Therefore, there arises problems such as “feathering” in which dots formed by the liquid droplets are disordered in the shape of whiskers and “color bleed” in which different colors of ink droplets are mixed together to make a color border unclear when they are adjacently ejected on a sheet. In addition, it takes time to dry the liquid droplets ejected on the sheet.
In order to deal with the above problems, as described in Patent Document 1, a heating unit is used before or after the ejection of liquid droplets so as to prevent feathering and accelerate the drying of ink.
Furthermore, as described in Patent Document 2, a pretreatment liquid that reacts with ink to prevent feathering is applied with an application roller. Also, as described in Patent Document 3, the pretreatment liquid is ejected from the liquid ejection head in mist form and applied.    Patent Document 1: JP-A-8-323977    Patent Document 2: JP-A-2002-137378    Patent Document 3: JP-A-2005-138502
However, when the heating unit is provided as described in Patent Document 1, the power consumption of an apparatus becomes large. Furthermore, when the pretreatment liquid is applied with the application roller and the liquid ejection head as described in Patent Documents 2 and 3, irregularities in the application of the pretreatment liquid are caused. In addition, since the liquid is excessively applied onto the sheet, the quick-drying property of the sheet after reacting with the ink is degraded. Particularly, the sheet is likely to be curled and deflected, which results in occurrence of jamming, etc.